Questions about lazersteve's cold nitric acid recipe

[Barren Realms 007]

New Question. How does anyone go about cleaning the salts out of your reaction vessel after cooling? After pouring off the newly made acid the salts are like a rock, I'm sure people aren't just throwing away glassware. ( The Acid works fine! )

Hot water works to redissolve it.

 

[ExNuke]

New Question. How does anyone go about cleaning the salts out of your reaction vessel after cooling? After pouring off the newly made acid the salts are like a rock, I'm sure people aren't just throwing away glassware. ( The Acid works fine! )

Hot water works to redissolve it.

Thanks BR, I just discovered that myself. I was just in to big a hurry, a few minutes on the hot plate and it dissolved, cold (room temp) water didn't appear to touch it. When all else fails, apply heat. Napalm or a flame thrower is a little over the top though.

 

[upcyclist]

New Question. How does anyone go about cleaning the salts out of your reaction vessel after cooling? After pouring off the newly made acid the salts are like a rock, I'm sure people aren't just throwing away glassware. ( The Acid works fine! ) I found Hy-Yield Nitrate of Soda at the local garden center @ $9.00 for 4 pounds. Even with Walmart Drain Cleaner sulfric acid it's a lot cheaper to make HNO3 than to pay the Hazmat shipping fee.

IIRC, they were water soluble. Hot water.

Edit: On the cheaper to make front, it all depends on what your time is worth. For now at least, I'm inclined to agree, at least for when I need just nitric. I think I'll stick with purchased nitric for AR, at least for final refinings (may use Poor Man's for first drop).

 

[HizHiNess]

Hi Everyone,

I just joined the forum and this is my first reply. Revering to lazersteve's cold nitric acid recipe here are a few suggestions. The process outlined takes sodium nitrate dissolves it in very hot water, adds sulfuric acid then cools the solution to precipitate the sodium sulfate from the solution. What remains is a solution of nitric acid that is contaminated with a little sodium sulfate.

Equation (not balanced)

NaNO3 + H2SO4 = Na2SO4 + HNO3

The process of the reaction goes almost to completion only when the solution is cooled to 0 degree C. The concentration of nitric acid produced is dependent upon the degree of completion of the reaction and the concentration of sodium nitrate in water that one begins with. If one uses 100 ml of water to dissolve the sodium nitrate and the reaction was 100 percent then the nitric acid formed will still be dissolved in 100 ml of water. Achieving azeotrope concentrations of nitric acid will require distilling the mixture.

However, one can tweak the basic reaction by substituting other nitrates for the source of the NO3 in nitric acid. A great help is the Solubility table From Wikipedia, the free encyclopedia. Here you can find the solubility of many different compounds at various temperatures. An ideal nitrate would be extremely soluble in very little water and the metal carrying the nitrate, its sulfate should be virtually insoluble. The reaction would go virtually to completion and the nitric acid produced would be minimally diluted with water.

Unfortunately, no such ideal metal nitrate exits, but some of them make better candidates than others. Here are my suggestions.

Strontium nitrate
Potassium nitrate

Over 95 grams of Strontium nitrate will dissolve in 100 ml of water at 80 degree C. When sulfuric acid is added (use extreme care, great amounts of heat is produced when adding sulfuric acid to water, especially when the water is close to boiling, splattering can occur, add the sulfuric acid slowly) strontium sulfate will be produced that is virtually insoluble thus driving the reaction to completion (solubility about 0.015 grams per 100 ml of water). The strontium sulfate precipitate can be filtered out of the solution leaving a solution of almost pure diluted nitric acid.

Almost 200 grams of potassium nitrate will dissolve in 100 ml of water at 90 degrees C. The potassium sulfate produced can be made to precipitate by cooling the solution to about 5 degree C or lower. The advantage of using potassium nitrate is in the concentration of the initial solution of potassium nitrate in water and the fact that the potassium sulfate produced is less soluble in water (higher temperatures).

Sources of materials

Hobby Chemical Supply for potassium nitrate (5lbs - $15.00 10 lbs. - $25.00)
for strontium nitrate (1lbs - $5.00)
for sodium nitrate (1lbs - $5.50)

Lowes Home Improvement Plumbing Department professional drain cleaner Sulfuric Acid 93% (1quart bottle - about $10.00)

 

[HizHiNess]

Hi Again,

Just wanted to post another suggestion.

Calcium Nitrate, available at Amazon at about $7.50 for a 5.00 lbs bag would also work very well. Ca(NO3)2 is extremely soluble in water. Large amounts of it can be dissolved (more than 100 grams in 100 ml of water). When Sulfuric Acid is added to a saturated solution of Calcium Nitrate, a precipitate of Calcium Sulfate hydrate will form. Only 0.265 grams or less of Hydrated Calcium Sulfate will dissolve in 100 ml of water. In addition, the solubility of Hydrated Calcium Sulfate is uniform over the range of liquid water. This will drive the reaction of adding Sulfuric Acid to a saturated solution of Calcium Nitrate highly to the right (completion). The Nitric Acid produced can be easily filtered from the Hydrated Calcium Sulfate. Since the solubility of Hydrated Calcium Sulfate is uniform over the temperature of liquid water, cooling of the solution is not needed.

See my previous post for sources of chemicals and other suggestions.

 

[Topher_osAUrus]

I dont think i would use strontium personally, what would you do with the waste?

Potassium nitrate i would, but only if my local shop was out of sodium.

Calcium I would stay away from, unless you are using it to recycle the sodium sulfate from the last batch. As calcium sulfate is VERY hard to get all of your nitric out of.
But, i guess there are a whole bunch of things you can use the plaster byproduct for.

There are a couple threads that cover these issues much better than i can with a couple quick sentences.

Stay safe.

Toph

 

[Shark]

The Nitric Acid produced can be easily filtered from the Hydrated Calcium Sulfate.

I would like to see or hear how that could be done, short of distilling it off. My experience with calcium nitrate was that it produced a very strong acid, but filtering was practically impossible by gravity filtering alone. Under vacuum filtering there was some still left behind trapped in the "plaster". Potassium nitrate or sodium nitrate has always worked well and performed well for me. I have a distilling rig now, but still haven't used it, might be getting time to give it a test run soon.

 

[ExNuke]

About distilling the product from the Cold Nitric Acid Recipe. I previously made a small batch with good results but I'm only hobby level playing with silver and have run out of scrap feed stock. Does anyone know if a Stainless Steel distilling rig would have any problems? I recently found a stainless still that I made a long time ago to distill water, it would be a lot less fragile than an all glass rig and I already have it, only need a couple of viton O rings to put it back in service.

 

[Ckestrada]

If the end result is weak dilute nitric acid could one heat or evaporate to get a higher concentration?

 

[upcyclist]

If the end result is weak dilute nitric acid could one heat or evaporate to get a higher concentration?

Personally, I don't like to evaporate/heat/distill nitric unless necessary.

Assuming you've used concentrated sulfuric, reacted fully, and followed the directions, you'll get decent strength nitric. You can use it straight when protocols on here call for a 50/50 mix of nitric and water. Heck, even if it's quite dilute, there's still uses for dilute nitric in our work*, so you could just leave it alone, use it for those things, and take another shot at the cold nitric procedure.

*For example, last night I used a stirring rod to break up chunks of cement silver that I had been drying. I also had moved a second batch into the same drying dish (same feedstock). Of course, the fine silver powder stuck to everything. So I rinsed the rod & jar in dilute nitric into the current batch of nitric digest. Easy peasy.

 

[HizHiNess]

Hi Virgil,

I think I may have a reason and a solution for your problem of not being able to dissolve the 170 grams of sodium nitrate in 100 ml of water. You mentioned that you boiled the water, measured off 100 ml, then added the sodium nitrate, and stirred.

Sodium nitrate is similar to ammonium nitrate in as much as both compounds absorb heat as they dissolve. The water was at 100 C when you poured it but when you started to dissolve the sodium nitrate, the temperature quickly fell. Sodium nitrate has a steep solubility curve. At lower temperatures much less can go into solution.

The solution is to add the sodium nitrate and then put the container (heat resistant glass) back into the microwave and carefully heat the sodium nitrate solution up to boiling again. Almost all of the sodium nitrate will go into solution.

Now comes the tricky and possible dangerous part. Immediately remove the dissolved sodium nitrate from the microwave and very carefully add the sulfuric acid. Add the acid in small increments. The resulting solution will boil and splatter (use a high walled container safety glasses and acid resistant clothing).

When all the sulfuric acid has been added, immediately stirr the resulting solution. Cap the solution and let the solution return to room temperature. Place the solution container into a zip lock plastic bag and place into the freezer.

When the temperature is at equilibrium, remove from freezer, and pour off or filter the thick liquid. This is the nitric acid you have made. The crystals at the bottom and sides of the container are the sodium sulfate that precipitated from the solution at the freezer temperature. The removal of the sodium sulfate pushes the reaction to produce the nitric acid.

 

[HizHiNess]

Hi Everyone,

My suggestions for using other metallic nitrates (Strontium Nitrate, Calcium Nitrate) for making nitric acid from sulfuric acid was to bypass the need to freeze the reacted products to obtain the nitric acid. Freezing is required when one reacts either sodium or potassium nitrate with sulfuric acid.

You are correct, Shark when you stated that calcium sulfate does not filter well (my error). However, if a small centrifuge is available, one should be able to separate most of the nitric acid from the calcium sulfate.

Here are some questions for the group.

Which nitrate (sodium nitrate or potassium nitrate) produces the strongest nitric acid using Lazersteve's cold nitric acid recipe?

Which nitrate (sodium nitrate or potassium nitrate) produces the easiest separation of the produced potassium sulfate or sodium sulfate from the nitric acid produced?

 

[TreySeaJax]

Hi,

First, I want to thank this board for encouraging me to study the posts. Read Hoke's book then re-read it several times.

Some day soon I am going to purchase some lab grade nitric acid. I hope to one day distill some super pure nitric. For now I am making my own with varied results.

Steve, I tried the recipe you posted with potassium nitrate. I used the Spectracide granules. I measured 220 grams and dissolved on low heat in 100 ml distilled h2o. Once dissolved, added 140 g drain opener h2so4.

I put it in the freezer and checked every 15 minutes. Maybe I should have pulled it earlier but it went from liquid to full of solid, potassium sulfate right? The liquid was hard to pour and filter. The yeild was about 70 ml that eventually came through.

So, there may be more nitric trapped inside the soild form. I am going to try to bust it up and dump it in the filter to see what else will come out.

The part I am very thankful for is, that is a much stronger nitric than what I usually make. Even if the 70 ml is all to expect, I will do it again. The whole process took less than an hour and a half.

Thanks for taking the time to help others!